A variable valve mechanism 90 of a conventional example (Patent Document 1) shown in FIGS. 6A to 8C includes a camshaft 91, an input arm 92, and an output arm 93. The camshaft 91 has a driving cam 91a mounted thereon so as to project therefrom. The input arm 92 swings when driven by the driving cam 91a. The output arm 93 is swingably mounted next to the input arm 92 and drives a valve 7 when swinging. As shown in FIGS. 6A and 6B, the variable valve mechanism 90 is switched to a drive mode (coupled state), or a mode in which the output arm 93 drives the valve 7, by coupling the input arm 92 and the output arm 93 via a switch pin 94 so that the input arm 92 and the output arm 93 swing together. As shown in FIGS. 7A and 7B, the variable valve mechanism 90 is switched to a non-drive or no-lift mode (uncoupled state), or a mode where driving of the valve 7 is stopped, by uncoupling the input arm 92 from the output arm 93.
As shown in FIG. 8C etc., the camshaft 91 further has a no-lift cam 91b (round cam) mounted thereon at a position corresponding to the output arm 93 so as to project from the camshaft 91. The size of the no-lift cam 91b corresponds to the base circle of the driving cam 91a. In addition to Patent Document 1, Patent Documents 2, 3, etc. describe a camshaft having projections such as a no-lift cam (round cam) or a lobe.